Let's do some math ..  Rounding examples of 7 random hypothetical purchases:
Case	Tag   Price	Sales   Tax %	Raw Total   Incl. Sales Tax	Rounded   to Penny	Rounded   to Nickel	Rounded   to Dime
Purchase #1	$94.28	4.281%	$98.3161	$98.32	$98.30	$98.30
Purchase #2	$163.30	11.136%	$181.4851	$181.49	$181.50	$181.50
Purchase #3	$66.71	11.721%	$74.5291	$74.53	$74.55	$74.50
Purchase #4	$146.76	5.482%	$154.8054	$154.81	$154.80	$154.80
Purchase #5	$225.57	5.536%	$238.0576	$238.06	$238.05	$238.10
Purchase #6	$120.40	6.208%	$127.8744	$127.87	$127.85	$127.90
Purchase #7	$34.64	7.199%	$37.1337	$37.13	$37.15	$37.10
7 purchase totals =	$851.66		$912.2014	$912.21	$912.20	$912.20